The ordinal and subclass classification of the Demospongiae (Porifera); appraisal of the present arrangement, and proposal of a new order

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Abstract
The criteria for subclass diagnosis within the Demospongiae are evaluated, with particular reference to dependence on oviparous or viviparous reproductive sequence as a primary characteristic in defining the three subclasses. Emphasis on reproductive pattern and larval type has permitted the development of a more natural classification than ever before. New evidence confirming the occurrence of oviparity in three groups previously classified with the viviparous Ceractinomorpha, coupled with histological, biochemical, and paleontological studies, requires that a new order be established and that the diagnosis of the Ceractinomorpha be amended. The new order Nepheliospongida is diagnosed, and the genera Petrosia, Strongylophora, Xestospongia, Oceanapia, Foliolina, Calyx, Vagocia, and Biminia are assigned to it. It is suggested that the ancient reproductive pattern in subclass Ceractinomorpha was oviparity, and that this condition has been retained in at least two divergent lines represented by the Nepheliospongida and the Verongida. More recent evolution, however, has been towards viviparity.